Here, we are big fans of LiveView. Every project we started since 2023 uses LiveView - no more JS nightmares. Working with LiveView is effortless and time-saving.
Getting started with the generated view and easy and fun. Once the application grows, there are some performance considerations to keep in mind. Here are some practical tips from our experience for better scalability and performance.
Efficient state
LiveView operates on the principle that each user's view is managed by a dedicated Elixir process. This process holds its state in the socket.assigns map. The size and efficiency of this state are important for scalability.
Minimizing assigns
Avoid storing large, complex data structures like deeply nested Ecto schemas or full query results. Only keep the data absolutely necessary for the current view. Large assigns increase the memory footprint for every single connected user, which can quickly become a problem at scale.
Use temporary_assigns for ephemeral data
For data that is only needed for a single render cycle—such as flash messages, search results, or form errors—use temporary_assigns. This way the data is automatically purged from memory after being rendered, preventing memory bloat in long-running LiveView processes.
Mastering the Rendering Engine
LiveView's core strength is its ability to send minimal, surgical updates to the client. You can enhance this by structuring your application to make the diffing process as efficient as possible.
Extract LiveComponents
Break down complex LiveViews into smaller, reusable LiveComponents. This isolates state and rendering logic. When a component's state changes, only that component and its children re-render, reducing the workload on the server and the amount of data sent over the wire.
Use Phoenix.LiveView.stream/4 for lists
For large, dynamic lists (like a real-time feed or a table with many rows), streams are a must-have. Nowadays, this is the out-of-the-box way autogenerated views render lists. Instead of diffing the entire list, streams allow you to surgically insert, delete, or update individual items. This is far more performant than re-rendering a huge list every time a single item changes.
Throttle high-frequency events
User actions like a phx-change on a search input can generate a high volume of events. Use client-side throttling or debouncing to limit how often these events are sent to the server, preventing it from being overwhelmed by unnecessary requests.
Asynchronous workflows
A LiveView process is lightweight, but it's still a single process. Any synchronous, long-running task will block it, causing the UI to freeze for the user.
Offload heavy tasks to background processes
Any operation that takes more than a few milliseconds—like generating a PDF, processing an image upload, or performing a complex report—should be offloaded. Use Elixir's Task module or a robust job queue like Oban to run these jobs in the background.
PubSub for real-time updates
Once a background job is complete, it can broadcast a message to a Phoenix PubSub topic. Your LiveView can subscribe to this topic and receive the result asynchronously. This allows to update the UI (e.g., replace a loading spinner with the final result) without ever blocking the LiveView process.
Database and query optimizations
The database is often the first bottleneck to appear as an application scales.
Optimize Ecto queries
Use Ecto.Query.select/2 to fetch only the columns you need from the database. Avoid loading entire schema structs when you only need a few fields.
Implement caching
For data that is frequently accessed but changes infrequently, implement a caching strategy. You can use an in-memory cache like ETS to reduce the load on your database.
Load balancing
Deploy multiple, independent Phoenix nodes behind a load balancer. Since LiveView relies on a persistent WebSocket connection, ensure your load balancer supports "sticky sessions" or consistent routing based on the user's connection ID to send subsequent requests from the same user to the same node.
Monitoring
You can't optimize what you can't measure.
Phoenix LiveDashboard
Use the built-in LiveDashboard to monitor your application in real time. It provides invaluable insights into process counts, memory usage, PubSub activity, and more, helping you identify bottlenecks.
Telemetry
Phoenix and LiveView emit rich telemetry events. Use tools to hook into these events and gather custom metrics on render times, event handler durations, and network payload sizes. This data is essential for making informed optimization decisions.
By applying these strategies, you can build a LiveView application that scales gracefully to handle a large and growing user base.